RESUMEN
AIMS: To examine the factors that are associated with changes in depression in people with type 2 diabetes living in 12 different countries. METHODS: People with type 2 diabetes treated in out-patient settings aged 18-65 years underwent a psychiatric assessment to diagnose major depressive disorder (MDD) at baseline and follow-up. At both time points, participants completed the Patient Health Questionnaire (PHQ-9), the WHO five-item Well-being scale (WHO-5) and the Problem Areas in Diabetes (PAID) scale which measures diabetes-related distress. A composite stress score (CSS) (the occurrence of stressful life events and their reported degree of 'upset') between baseline and follow-up was calculated. Demographic data and medical record information were collected. Separate regression analyses were conducted with MDD and PHQ-9 scores as the dependent variables. RESULTS: In total, there were 7.4% (120) incident cases of MDD with 81.5% (1317) continuing to remain free of a diagnosis of MDD. Univariate analyses demonstrated that those with MDD were more likely to be female, less likely to be physically active, more likely to have diabetes complications at baseline and have higher CSS. Mean scores for the WHO-5, PAID and PHQ-9 were poorer in those with incident MDD compared with those who had never had a diagnosis of MDD. Regression analyses demonstrated that higher PHQ-9, lower WHO-5 scores and greater CSS were significant predictors of incident MDD. Significant predictors of PHQ-9 were baseline PHQ-9 score, WHO-5, PAID and CSS. CONCLUSION: This study demonstrates the importance of psychosocial factors in addition to physiological variables in the development of depressive symptoms and incident MDD in people with type 2 diabetes. Stressful life events, depressive symptoms and diabetes-related distress all play a significant role which has implications for practice. A more holistic approach to care, which recognises the interplay of these psychosocial factors, may help to mitigate their impact on diabetes self-management as well as MDD, thus early screening and treatment for symptoms is recommended.
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Trastorno Depresivo Mayor/diagnóstico , Diabetes Mellitus Tipo 2/complicaciones , Tamizaje Masivo/métodos , Calidad de Vida , Estrés Psicológico/etiología , Adulto , Anciano , Trastorno Depresivo Mayor/epidemiología , Trastorno Depresivo Mayor/psicología , Diabetes Mellitus Tipo 2/epidemiología , Diabetes Mellitus Tipo 2/psicología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Cuestionario de Salud del Paciente , Estudios Prospectivos , Escalas de Valoración Psiquiátrica/estadística & datos numéricos , Distrés Psicológico , Estrés Psicológico/epidemiología , Encuestas y Cuestionarios , Adulto JovenRESUMEN
To conduct a systematic review and meta-analysis of longitudinal studies assessing the bi-directional association between depression and diabetes macrovascular and microvascular complications. Embase, Medline and PsycINFO databases were searched from inception through 27 November 2017. A total of 4592 abstracts were screened for eligibility. Meta-analyses used multilevel random/mixed-effects models. Quality was assessed using the Newcastle-Ottawa scale. Twenty-two studies were included in the systematic review. Sixteen studies examined the relationship between baseline depression and incident diabetes complications, of which nine studies involving over one million participants were suitable for meta-analysis. Depression was associated with an increased risk of incident macrovascular (HR = 1.38; 95% CI: 1.30-1.47) and microvascular disease (HR = 1.33; 95% CI: 1.25-1.41). Six studies examined the association between baseline diabetes complications and subsequent depression, of which two studies involving over 230 000 participants were suitable for meta-analysis. The results showed that diabetes complications increased the risk of incident depressive disorder (HR = 1.14; 95% CI: 1.07-1.21). The quality analysis showed increased risk of bias notably in the representativeness of selected cohorts and ascertainment of exposure and outcome. Depression in people with diabetes is associated with an increased risk of incident macrovascular and microvascular complications. The relationship between depression and diabetes complications appears bi-directional. However, the risk of developing diabetes complications in depressed people is higher than the risk of developing depression in people with diabetes complications. The underlying mechanisms warrant further research.
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Depresión/epidemiología , Complicaciones de la Diabetes/psicología , Depresión/complicaciones , Angiopatías Diabéticas/psicología , Humanos , Estudios Longitudinales , MEDLINE , Microvasos , Factores de RiesgoRESUMEN
AIM: This study investigates the relationship between personality dimensions and job satisfaction. BACKGROUND: The shortage of nurses, and those voluntarily leaving their jobs, continues to be a problem affecting the delivery of healthcare all over the world, including anaesthesia. If it is found that nurse anaesthetists with certain personality types have high levels of job satisfaction, the information may be helpful for the retention of nurse anaesthetists. METHODS: A questionnaire was distributed amongst Dutch nurse anaesthetists. Factor and multiple regression analyses were performed to reveal personality dimensions and their impact on job satisfaction. RESULTS: Nine hundred and twenty-three questionnaires were completed and analysed (46% response rate). Two personality dimensions -'easy going' and 'orderly'- explained 3.5% of the variance in job satisfaction. CONCLUSION: Personality dimensions as measured with the Myers-Briggs Type Indicator (MBTI) are only minimally relevant in predicting job satisfaction amongst Dutch nurse anaesthetists. IMPLICATIONS FOR NURSING MANAGEMENT: Before using personality traits as a selection tool for retaining employees, it is important to understand the relationship of particular personalities to job satisfaction; it is also important to know which combination of personality traits is likely to create a highly cohesive work group.
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Satisfacción en el Trabajo , Enfermeras Anestesistas/psicología , Personalidad , Adulto , Actitud del Personal de Salud , Estudios Transversales , Femenino , Encuestas de Atención de la Salud , Humanos , Masculino , Persona de Mediana Edad , Modelos Psicológicos , Países Bajos , Enfermeras Anestesistas/estadística & datos numéricos , Inventario de Personalidad , Análisis de Regresión , Encuestas y CuestionariosRESUMEN
BACKGROUND: An ageing population, combined with a shortage of health-care professionals, can result in a decrease in the capacity of health-care systems. Therefore, it is important to explore possible solutions for this problem. By finding methods to increase job satisfaction, it may be possible to retain employees within their profession. In this study, we examined events, their influence on emotions and, consequently, the effect of these emotions on job satisfaction. We attempted to answer the question: Which events and emotions influence job satisfaction? METHODS: We collected data on events and emotions, and their effects on job satisfaction, amongst Dutch nurse anaesthetists. Participants (n = 314) were asked to complete two questionnaires about events, emotions and job satisfaction at two different times during an average working day. RESULTS: One hundred thirty-two nurse anaesthetists from 24 Dutch hospitals participated. Both positive and negative events were significant in the development of positive and negative emotions at the end of the working day. Positive emotions at the end of the working day contributed significantly to job satisfaction. Negative emotions did not have a significant effect on job satisfaction. CONCLUSIONS: The mediating role of positive emotions in relation to positive and negative events should be taken into account in managing job satisfaction amongst Dutch nurse anaesthetists. Further research is necessary to determine whether the relationship between events and emotions provides a foundation for developing a more positive working atmosphere, and also to explore how hospitals can trigger positive emotions to increase job satisfaction.
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Emociones , Satisfacción en el Trabajo , Enfermeras Anestesistas , Adulto , Femenino , Encuestas de Atención de la Salud , Humanos , Masculino , Modelos Psicológicos , Países Bajos , Análisis de Regresión , IncertidumbreRESUMEN
BACKGROUND: To meet the increasing demand for healthcare providers, it is crucial to recruit and retain more nurse anaesthetists (NAs). The majority of NAs in the Netherlands are >45 years old, and retaining them in their jobs is very important. This study investigates the relationships among burnout, physical health and job satisfaction among Dutch NAs. METHODS: Two thousand NAs working in Dutch hospitals were invited to participate in this online questionnaire. We tested the relationships among burnout, psychosomatic symptoms, sickness absence, perceived general health and job satisfaction. RESULTS: Nine hundred and twenty-three questionnaires were completed and analysed (46% response rate). Burnout and psychosomatic symptoms were negatively associated with job satisfaction, and predicted 27% of job satisfaction. Perceived general health was positively and sickness absence was negatively related to job satisfaction. Older NAs had a higher incidence of burnout than their younger counterparts. CONCLUSIONS: The results confirmed the importance of a healthy psychosocial work environment for promoting job satisfaction. To prevent burnout, further research is necessary to determine the factors causing stress. These findings may also apply to anaesthesiologists who share many tasks and work in close cooperation with NAs.
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Agotamiento Profesional/psicología , Satisfacción en el Trabajo , Enfermeras Anestesistas/psicología , Trastornos Psicofisiológicos/etiología , Adulto , Anestesiología , Agotamiento Profesional/epidemiología , Femenino , Humanos , Masculino , Salud Mental , Persona de Mediana Edad , Países Bajos/epidemiología , Trastornos Psicofisiológicos/epidemiología , Análisis de Regresión , Medición de Riesgo , Encuestas y Cuestionarios , Adulto JovenRESUMEN
OBJECTIVES: This study examined the importance of one's social work environment in the light of prevention of premature leave from the nursing profession. A research model with social support (from direct supervisor and close colleagues) as predictor and intention to leave as the dependent variable has been tested, while controlling for job satisfaction and age. Moreover, we have studied the impact of nurses' age upon the prevalence of social support from both parties. PARTICIPANTS: Data were obtained from 17,524 registered female nurses working in hospitals throughout Europe (Belgium, Germany, Finland, France, Italy, The Netherlands, Poland, and Slovakia). RESULTS: Our findings indicated that a lack of job satisfaction is an important risk factor in the light of nurses' turnover as for most countries the intention to leave cannot be buffered by social support from one's close colleagues. However, in general, social support from one's direct superior appeared to contribute negatively to the intention to leave the profession, over and above job satisfaction and age. As regards age effects, in line with our expectation, we have found a significant negative relationship between age and social support from close colleagues, while the hypothesis regarding the relationship between age and supervisory support could not be confirmed. CONCLUSIONS: Given its importance in the light of preventing premature leave, we advocate not to neglect the possible positive effects of social support from important key figures like nurses' direct supervisor and close colleagues. It is necessary for health care institutions to carefully pay attention to finding opportunities to obtain more social support for all staff members. In Section 5, limitations and practical implications of this study are dealt with.
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Personal de Enfermería en Hospital/psicología , Apoyo Social , Europa (Continente) , Femenino , Humanos , Relaciones Interprofesionales , Satisfacción en el TrabajoRESUMEN
The influence of intensified and reduced training on nocturnal growth hormone (GH) secretion and elimination dynamics was studied in young (1.5 yr) Standardbred geldings to detect potential markers indicative for early overtraining. Ten horses trained on a treadmill for 32 wk in age-, breed-, and gender-matched fixed pairs. Training was divided into four phases (4, 18, 6, and 4 wk, respectively): 1) habituation to high-speed treadmill trotting, 2) normal training, in which speed and duration of training sessions were gradually increased, 3) in this phase, the horses were divided into 2 groups: control (C) and intensified trained (IT) group. In IT, training intensity, duration, and frequency were further increased, whereas in control these remained unaltered, and 4) reduced training (RT). At the end of phases 2, 3, and 4, blood was sampled overnight every 5 min for 8 h for assessment of GH secretory dynamics using pulse detection, deconvolution analysis, and approximate entropy (ApEn). Intensified training induced overtraining (performance decreased by 19% compared with C), which was associated with an increase in concentration peaks number (3.6 vs. 2.0, respectively), a smaller peak secretion pattern with a prolonged half-life (15.2 vs. 7.3 min, respectively), and an increased ApEn (0.89 vs. 0.49, respectively). RT did not lead to full recovery for the overtrained horses. The increased irregularity of nocturnal GH pulsatility pattern is indicative of a loss of coordinated control of GH regulation. Longer phases of somatostatin withdrawal are hypothesized to be the underlying mechanism for the observed changes in GH pulsatility pattern.
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Hormona del Crecimiento/metabolismo , Caballos/fisiología , Condicionamiento Físico Animal/fisiología , Descanso/fisiología , Animales , Prueba de Esfuerzo , Semivida , Factor I del Crecimiento Similar a la Insulina/metabolismo , Ácido Láctico/sangre , Masculino , Orquiectomía , Factores de TiempoRESUMEN
We review the work carried out within the eMinerals project to develop eScience solutions that facilitate a new generation of molecular-scale simulation work. Technological developments include integration of compute and data systems, developing of collaborative frameworks and new researcher-friendly tools for grid job submission, XML data representation, information delivery, metadata harvesting and metadata management. A number of diverse science applications will illustrate how these tools are being used for large parameter-sweep studies, an emerging type of study for which the integration of computing, data and collaboration is essential.
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Clima , Internet , Minerales/química , Modelos Químicos , Modelos Moleculares , Ciencia/métodos , Programas Informáticos , Simulación por ComputadorRESUMEN
We describe RMCS as one of the first tools for grid computing that integrates data and metadata management into a single job submission system. The system is easy to use, with client tools that are easy to install. Although the RMCS system was developed as a prototype, it is now in production use and a number of scientific studies have been completed using it.
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Conducta Cooperativa , Sistemas de Administración de Bases de Datos/tendencias , Bases de Datos Factuales/tendencias , Ecología/métodos , Almacenamiento y Recuperación de la Información/tendencias , Internet , Modelos Teóricos , Programas Informáticos , Simulación por Computador , Ecología/tendencias , Difusión de la Información/métodos , Integración de Sistemas , Interfaz Usuario-ComputadorRESUMEN
With an ever increasing number of patients and more demanding health care system it is important to keep nurse anesthetists as mentally and physically fit as possible. Especially with a shortage of nurse anesthetists it is important to know which work context factors are important for maintaining a healthy balance between the nurse anesthetist and his work environment. This study is the first to determine which work context factors of nurse anesthetists are most relevant for a healthy work environment. A questionnaire survey, containing work related items, was distributed among all nurse anesthetists working in Dutch hospitals. All together 882 questionnaires (response rate 44%) were completed and analyzed, including factor analysis for the discriminating work context factors. Four discriminating work context factors (career/rewards, relation with supervisor, task contents and social environment) were found to be relevant, explaining 48% of the variance in work context. All four work context factors are considered to be job resources, although not hospital related. Supervisors (head nurses) interpret these work context factors differently from nurse anesthetists, which can result in dissatisfaction of the latter group. Nurse anesthetists participate more in sub-functions and activities in larger peripheral and academic anesthesia departments. Smaller anesthesia departments require nurse anesthetists to be more flexible and perform many different functions within the anesthesia domain.
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Actitud del Personal de Salud , Enfermeras Anestesistas/psicología , Supervisión de Enfermería/estadística & datos numéricos , Autonomía Profesional , Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Países Bajos , Enfermeras Anestesistas/estadística & datos numéricos , Encuestas y Cuestionarios , Lugar de TrabajoRESUMEN
Desmoid tumors are fibromatous lesions occurring both sporadically and in patients with familial adenomatous polyposis (FAP). Because of the association of these tumors with the hereditary colorectal cancer syndrome FAP we set out to define the molecular events driving desmoid tumorigenesis, hypothezising these might be identical to events driving colorectal tumorigenesis. We found that whereas FAP-associated desmoid tumors are caused by germline APC mutations followed by somatic inactivation of the wild-type APC allele, sporadic desmoids are usually characterized by oncogenic mutations in the b-catenin gene, both identical molecular alterations to those found in the vast majority of colorectal cancers. Next we set out to investigate the cellular pathways activated by these mutations, and identified activation of the Wnt signaling pathway in desmoid tumors. Wnt signaling modulates expression of developmental genes and cell fate via beta-catenin, and has been implicated in many cancer types. Currently we are investigating tissue-specific downstream effectors of the Wnt pathway that might be responsible for the behaviour of these invasive fibrous tumors. Our findings also point to a role for this pathway in the regulation of normal myofibroblast proliferation and suggest novel treatments in desmoid tumors and other fibrous proliferative disorders.
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Poliposis Adenomatosa del Colon/genética , Proteínas del Citoesqueleto/genética , Fibromatosis Agresiva/genética , Predisposición Genética a la Enfermedad , Polimorfismo Genético , Transactivadores/genética , Poliposis Adenomatosa del Colon/epidemiología , Poliposis Adenomatosa del Colon/fisiopatología , Femenino , Fibromatosis Agresiva/epidemiología , Fibromatosis Agresiva/fisiopatología , Regulación Neoplásica de la Expresión Génica , Genes APC , Humanos , Incidencia , Masculino , Mutación , Polimorfismo Conformacional Retorcido-Simple , Pronóstico , Medición de Riesgo , Sensibilidad y Especificidad , Índice de Severidad de la Enfermedad , Transducción de Señal , beta CateninaRESUMEN
We determined the oxygen isotope fractionation in expired alveolar gas relative to inspired air (delta(A-I)) in eight young, healthy subjects at rest and at five levels of exercise up to maximal workload both before and after a training period of about 4 weeks which increased maximum oxygen uptake by about 10%. The data for delta(A-I) were used to compute the relative difference (deltaU) between the resistances of 16O18O and 16O2 for oxygen transport from the alveolar space and utilization in the mitochondria. Prior to training, deltaU decreased from 15 per thousand at rest to 5 per thousand at the highest level of exercise and after training from 12 to 5 per thousand. The difference between the results for deltaU before and after training was significant for rest (P < or = 5) but not for exercise conditions. Accordingly, we conclude that for exercise conditions the non-fractionating oxygen transport by blood flow to and the fractionating oxygen transport by diffusion in the muscles have improved by training to more or less the same degree. The decrease in deltaU in rest after training suggests that oxygen transport by diffusion in other tissues also benefits from the effects of training.
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Ejercicio Físico/fisiología , Consumo de Oxígeno/fisiología , Oxígeno/metabolismo , Esfuerzo Físico/fisiología , Capacidad de Difusión Pulmonar/fisiología , Adulto , Transporte Biológico Activo/fisiología , Humanos , Marcaje Isotópico , Masculino , Modelos Biológicos , Isótopos de Oxígeno , Aptitud Física/fisiología , Ventilación Pulmonar/fisiología , Valores de ReferenciaRESUMEN
Desmoid tumours are locally invasive soft tissue tumours in which beta-catenin mediated TCF-dependent transcription is activated. The role of soluble factors secreted by the myofibroblastic desmoid tumour, which could stimulate tumour invasiveness, was investigated. Using collagen gel invasion assays, the presence of factors stimulating invasion in desmoid conditioned media (CM) could be established. Since matrix metalloproteinases (MMPs) have been implicated in the process of tumoral invasion, the expression levels of the MMP family members were evaluated. Quantitative reverse transcription-PCR was used to determine the expression levels of MMP1, MMP2, MMP3, MMP7, MMP11, MMP12, MMP13, MMP14 and the inhibitors TIMP1, TIMP2 and TIMP3. Besides overexpression of MMP7, a known TCF-dependent target gene, a striking upregulation of the expression levels of MMP1, MMP3, MMP11, MMP12 and MMP13 in desmoid tumours, compared to unaffected fibroblasts from the same patients, was found. Treating the CM of desmoids with a synthetic and a physiologic MMP inhibitor reduced the invasion-stimulating capacity of the desmoid CM by approximately 50%. These results suggest the involvement of soluble factors, released by the desmoid cells, in stimulating invasion and implicate the MMPs as facilitators of invasion.
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Fibromatosis Agresiva/enzimología , Metaloproteinasas de la Matriz/metabolismo , Medios de Cultivo Condicionados , Humanos , Técnicas para Inmunoenzimas , Invasividad Neoplásica , Análisis por Matrices de Proteínas , Células Tumorales CultivadasRESUMEN
The HXT5 gene encodes a functional hexose transporter that has moderate affinity for glucose (K(m)=10 mM), moderate to low affinity for fructose (K(m)=40 mM) and low affinity for mannose (K(m)>100 mM). The sole presence of Hxt5p in an otherwise hexose transport null mutant is sufficient to sustain a flux through glycolysis from glucose to fermentative products. However, the presence of HXT5 as the sole hexose transporter gene results in extremely poor growth on glucose, which suggests the involvement of glucose repression in the transcriptional regulation of HXT5. From Northern blot analysis on the members of the HXT family and studies with HXT5 tagged with the green fluorescent protein (GFP), it is evident that HXT5 is transcribed and translated during conditions of relatively slow growth, during growth on non-fermentable carbon sources and in particular during sporulation. In wild-type batch cultivations on fermentable carbon sources, Hxt5p is abundant in stationary phase or after depletion of the fermentable carbon source, which seems independent of the carbon source. The deletion of HXT5 does not result in a clear phenotype. A shift of stationary phase cells to fresh glucose medium resulted in somewhat slower resumption of growth in the hxt5 deletion strain compared to the wild-type strain. The abundance of Hxt5p during stationary phase, sporulation and low glucose conditions suggests that HXT5 is a 'reserve' transporter, which might be involved in the initial uptake of glucose after the appearance of glucose. Other possible functions of the protein encoded by HXT5 will be discussed in the context of the results.
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Proteínas Fúngicas/fisiología , Regulación Fúngica de la Expresión Génica/fisiología , Proteínas de Transporte de Monosacáridos/fisiología , Saccharomyces cerevisiae/fisiología , Northern Blotting , Proteínas Fúngicas/genética , Regulación Fúngica de la Expresión Génica/genética , Glucosa/metabolismo , Proteínas Fluorescentes Verdes , Cinética , Proteínas Luminiscentes/química , Microscopía Fluorescente , Microscopía de Contraste de Fase , Proteínas de Transporte de Monosacáridos/genética , Mutagénesis , Reacción en Cadena de la Polimerasa , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismoRESUMEN
High-affinity hexose transport is required for efficient utilization of low hexose concentrations by the baker's yeast Saccharomyces cerevisiae. These low concentrations occur during the late exponential phase of batch growth on hexoses, during hexose-limited chemostat or fed-batch culture, or during growth on sugars such as sucrose and raffinose that are hydrolysed to hexoses outside the cell. The expression of the Hxt7 high-affinity glucose transporter of S. cerevisiae was examined during batch growth on glucose medium in a wild-type strain and a strain expressing only HXT7 (i.e. with null mutations in HXT1-HXT6). In the wild-type strain, HXT7 transcription was repressed at high glucose and was detected when the glucose in the culture approached depletion. In the HXT7-only strain, transcription of HXT7 was constitutive throughout the glucose growth phase and was increased further at low glucose concentrations. After glucose depletion, the levels of HXT7 mRNA declined rapidly in both strains. In contrast, the Hxt7 protein was relatively stable after glucose depletion. By monitoring the subcellular localization of an Hxt7::GFP fusion protein it was observed that Hxt7 was localized in the plasma membrane, even when expressed at high glucose concentrations in the HXT7-only strain. After glucose depletion Hxt7 was gradually endocytosed and targeted to the vacuole for degradation. The Hxt7::GFP fusion protein was a fully functional hexose transporter with a catalytic centre activity of approximately 200/sec. It is concluded that repression of HXT7 and degradation of Hxt7 at high glucose concentrations is dependent on a high glucose transport capacity.
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Proteínas Fúngicas/metabolismo , Regulación Fúngica de la Expresión Génica , Glucosa/metabolismo , Proteínas de Transporte de Monosacáridos/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Medios de Cultivo , Proteínas Fúngicas/genética , Proteínas Fluorescentes Verdes , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Proteínas de Transporte de Monosacáridos/genética , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Saccharomyces cerevisiae/crecimiento & desarrolloRESUMEN
In previous studies it was shown that deletion of the HXK2 gene in Saccharomyces cerevisiae yields a strain that hardly produces ethanol and grows almost exclusively oxidatively in the presence of abundant glucose. This paper reports on physiological studies on the hxk2 deletion strain on mixtures of glucose/sucrose, glucose/galactose, glucose/maltose and glucose/ethanol in aerobic batch cultures. The hxk2 deletion strain co-consumed galactose and sucrose, together with glucose. In addition, co-consumption of glucose and ethanol was observed during the early exponential growth phase. In S.cerevisiae, co-consumption of ethanol and glucose (in the presence of abundant glucose) has never been reported before. The specific respiration rate of the hxk2 deletion strain growing on the glucose/ethanol mixture was 900 micromol.min(-1).(g protein)(-1), which is four to five times higher than that of the hxk2 deletion strain growing oxidatively on glucose, three times higher than its parent growing on ethanol (when respiration is fully derepressed) and is almost 10 times higher than its parent growing on glucose (when respiration is repressed). This indicates that the hxk2 deletion strain has a strongly enhanced oxidative capacity when grown on a mixture of glucose and ethanol.
Asunto(s)
Metabolismo de los Hidratos de Carbono , Etanol/metabolismo , Eliminación de Gen , Glucosa/metabolismo , Hexoquinasa/genética , Saccharomyces cerevisiae/metabolismo , Dióxido de Carbono/metabolismo , Medios de Cultivo , Galactosa/metabolismo , Genes Fúngicos , Glucosa/análogos & derivados , Glucosa/farmacología , Hexoquinasa/metabolismo , Maltosa/metabolismo , Oxidación-Reducción , Consumo de Oxígeno , Saccharomyces cerevisiae/enzimología , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crecimiento & desarrollo , Sacarosa/metabolismoRESUMEN
Hexokinase II is an enzyme central to glucose metabolism and glucose repression in the yeast Saccharomyces cerevisiae. Deletion of HXK2, the gene which encodes hexokinase II, dramatically changed the physiology of S. cerevisiae. The hxk2-null mutant strain displayed fully oxidative growth at high glucose concentrations in early exponential batch cultures, resulting in an initial absence of fermentative products such as ethanol, a postponed and shortened diauxic shift, and higher biomass yields. Several intracellular changes were associated with the deletion of hexokinase II. The hxk2 mutant had a higher mitochondrial H(+)-ATPase activity and a lower pyruvate decarboxylase activity, which coincided with an intracellular accumulation of pyruvate in the hxk2 mutant. The concentrations of adenine nucleotides, glucose-6-phosphate, and fructose-6-phosphate are comparable in the wild type and the hxk2 mutant. In contrast, the concentration of fructose-1,6-bisphosphate, an allosteric activator of pyruvate kinase, is clearly lower in the hxk2 mutant than in the wild type. The results suggest a redirection of carbon flux in the hxk2 mutant to the production of biomass as a consequence of reduced glucose repression.
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Eliminación de Gen , Hexoquinasa/genética , Saccharomyces cerevisiae/enzimología , Saccharomyces cerevisiae/fisiología , Aerobiosis , Medios de Cultivo , Glucosa/metabolismo , Hexoquinasa/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismoRESUMEN
A large proportion of the 6,000 genes present in the genome of Saccharomyces cerevisiae, and of those sequenced in other organisms, encode proteins of unknown function. Many of these genes are "silent, " that is, they show no overt phenotype, in terms of growth rate or other fluxes, when they are deleted from the genome. We demonstrate how the intracellular concentrations of metabolites can reveal phenotypes for proteins active in metabolic regulation. Quantification of the change of several metabolite concentrations relative to the concentration change of one selected metabolite can reveal the site of action, in the metabolic network, of a silent gene. In the same way, comprehensive analyses of metabolite concentrations in mutants, providing "metabolic snapshots," can reveal functions when snapshots from strains deleted for unstudied genes are compared to those deleted for known genes. This approach to functional analysis, using comparative metabolomics, we call FANCY-an abbreviation for functional analysis by co-responses in yeast.
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Metabolismo Energético/genética , Genoma Fúngico , Genómica/métodos , Mutación , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Nucleótidos de Adenina/metabolismo , Análisis por Conglomerados , Genotipo , Hexosafosfatos/metabolismo , Fenotipo , Piruvatos/metabolismo , Saccharomyces cerevisiae/crecimiento & desarrolloRESUMEN
Glucose transport kinetics and mRNA levels of different glucose transporters were determined in Saccharomyces cerevisiae strains expressing different sugar kinases. During exponential growth on glucose, a hxk2 null strain exhibited high-affinity hexose transport associated with an elevated transcription of the genes HXT2 and HXT7, encoding high-affinity transporters, and a diminished expression of the HXT1 and HXT3 genes, encoding low-affinity transporters. Deletion of HXT7 revealed that the high-affinity component is mostly due to HXT7; however, a previously unidentified very-high-affinity component (K(m) = 0.19 mM) appeared to be due to other factors. Expression of genes encoding hexokinases from Schizosaccharomyces pombe or Yarrowia lipolytica in a hxk1 hxk2 glk1 strain prevented derepression of the high-affinity transport system at high concentrations of glucose.
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Proteínas Fúngicas/genética , Regulación Fúngica de la Expresión Génica , Glucosa/metabolismo , Hexoquinasa/metabolismo , Proteínas de Transporte de Monosacáridos/genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Transporte Biológico , Proteínas Facilitadoras del Transporte de la Glucosa , Hexoquinasa/genética , Cinética , Proteínas de la Membrana/genética , Saccharomyces cerevisiae/crecimiento & desarrollo , Saccharomyces cerevisiae/metabolismoRESUMEN
This paper examines whether the in vivo behavior of yeast glycolysis can be understood in terms of the in vitro kinetic properties of the constituent enzymes. In nongrowing, anaerobic, compressed Saccharomyces cerevisiae the values of the kinetic parameters of most glycolytic enzymes were determined. For the other enzymes appropriate literature values were collected. By inserting these values into a kinetic model for glycolysis, fluxes and metabolites were calculated. Under the same conditions fluxes and metabolite levels were measured. In our first model, branch reactions were ignored. This model failed to reach the stable steady state that was observed in the experimental flux measurements. Introduction of branches towards trehalose, glycogen, glycerol and succinate did allow such a steady state. The predictions of this branched model were compared with the empirical behavior. Half of the enzymes matched their predicted flux in vivo within a factor of 2. For the other enzymes it was calculated what deviation between in vivo and in vitro kinetic characteristics could explain the discrepancy between in vitro rate and in vivo flux.